Spektor Kristina, Kohlmann Holger, Druzhbin Dmitrii, Crichton Wilson A, Bhat Shrikant, Simak Sergei I, Vekilova Olga Yu, Häussermann Ulrich
Inorganic Chemistry, Faculty for Chemistry and Mineralogy, Leipzig University, Leipzig, Germany.
Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
Front Chem. 2023 Sep 8;11:1251774. doi: 10.3389/fchem.2023.1251774. eCollection 2023.
Hydrogenation reactions at gigapascal pressures can yield hydrogen-rich materials with properties relating to superconductivity, ion conductivity, and hydrogen storage. Here, we investigated the ternary Na-Si-H system by computational structure prediction and synchrotron diffraction studies of reaction mixtures NaH-Si-H at 5-10 GPa. Structure prediction indicated the existence of various hypervalent hydridosilicate phases with compositions NaSiH (m = 1-3) at comparatively low pressures, 0-20 GPa. These ternary Na-Si-H phases share, as a common structural feature, octahedral SiH complexes which are condensed into chains for m = 1 and occur as isolated species for m = 2, 3. studies demonstrated the formation of the double salt Na[SiH]H (NaSiH, m = 3) containing both octahedral SiH moieties and hydridic H. Upon formation at elevated temperatures (>500°C), NaSiH attains a tetragonal structure (4/, = 2) which, during cooling, transforms to an orthorhombic polymorph (, = 4). Upon decompression, -NaSiH was retained to approx. 4.5 GPa, below which a further transition into a yet unknown polymorph occurred. NaSiH is a new representative of yet elusive hydridosilicate compounds. Its double salt nature and polymorphism are strongly reminiscent of fluorosilicates and germanates.
在吉帕斯卡压力下的氢化反应能够产生具有与超导性、离子导电性和储氢相关性质的富氢材料。在此，我们通过计算结构预测以及对反应混合物NaH-Si-H在5-10吉帕斯卡压力下的同步加速器衍射研究，对三元Na-Si-H体系进行了研究。结构预测表明，在相对较低的压力（0-20吉帕斯卡）下存在各种组成式为NaSiH （m = 1-3）的高价氢硅酸盐相。这些三元Na-Si-H相具有一个共同的结构特征，即八面体SiH 络合物，对于m = 1，它们缩合形成链状结构，而对于m = 2、3，则以孤立的物种形式存在。研究表明形成了同时包含八面体SiH 部分和氢化物H的复盐Na[SiH]H（NaSiH，m = 3）。在高温（>500°C）下形成时，NaSiH具有四方结构（4/， = 2），在冷却过程中转变为正交多晶型物（， = 4）。减压时，-NaSiH保持到约4.5吉帕斯卡，低于此压力会进一步转变为一种未知的多晶型物。NaSiH是难以捉摸的氢硅酸盐化合物的一个新代表。它的复盐性质和多晶型性强烈让人联想到氟硅酸盐和锗酸盐。
